"Clinical sciences, and in particular neuropsychology, also played a prominent role in helping usher in a new willingness to tackle the problem of consciousness. Various unusual syndromes came to light in the latter half of the 20th century, and these syndromes seemed to demand an explanation in terms of consciousness. Blindsight is a good example: In this syndrome, patients with lesions to the occipital lobe of the brain are phenomenologically blind, but can nonetheless perform normally on a number of visual tasks. Another example is amnesia, in which people who are phenomenologically amnesic as a result of damage to medial temporal lobes or the diencephalon can acquire, retain, and recover information without awareness. Similar examples emerged in other domains, and it soon became clear that processes under conscious control complement, or compete with, unconscious processes in the control of cognition and behavior. These issues are also beginning to play a major role in the rigorous, scientific analysis of psychopathology, the one field in which concerns with the role of conscious and unconscious processes have played a steady role since Freud."

Consciousness: An Introduction - Philip David Zelazo, Morris Moscovitch, and Evan Thompson

"The massive redeployment hypothesis (MRH) is a theory about the functional topography of the human brain, offering a middle course between strict localization on the one hand, and holism on the other. Central to MRH is the claim that cognitive evolution proceeded in a way analogous to component reuse in software engineering, whereby existing components—originally developed to serve some specific purpose—were used for new purposes and combined to support new capacities, without disrupting their participation in existing programs. If the evolution of cognition was indeed driven by such exaptation, then we should be able to make some specific empirical predictions regarding the resulting functional topography of the brain."

Massive Redeployment, Exaptation, and the Functional Integration of Cognitive Operations - Michael L. Anderson

Dopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D1, D2, D3, D4, and D5, and their variants. Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area. Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary. Dopamine can be supplied as a medication that acts on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure. However, because dopamine cannot cross the blood-brain barrier, dopamine given as a drug does not directly affect the central nervous system. To increase the amount of dopamine in the brains of patients with diseases such as Parkinson's disease and dopa-responsive dystonia, L-DOPA (levodopa), which is the precursor of dopamine, can be given because it can cross the blood-brain barrier.

http://en.wikipedia.org/wiki/Dopamine

Serotonin is a monoamine neurotransmitter. It is found extensively in the gastrointestinal tract of animals, and about 80 to 90 percent of the human body's total serotonin is located in the enterochromaffin cells in the gut, where it is used to regulate intestinal movements. The remainder is synthesized in serotonergic neurons in the central nervous system (CNS) where it has various functions, including control of appetite, mood and anger. Serotonin is found not only in animals, but also in fungi and plants, including fruits and vegetables.

http://en.wikipedia.org/wiki/Serotonin

The chemical compound acetylcholine (often abbreviated ACh) is a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the motor division of the somatic nervous system. (Sensory neurons use glutamate and various peptides at their synapses.) Acetylcholine is also the principal neurotransmitter in all autonomic ganglia.

http://en.wikipedia.org/wiki/Acetylcholine

γ-Aminobutyric acid (GABA) is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays an important role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone. In insect species GABA acts only on excitatory nerve receptors. Although chemically it is an amino acid, GABA is rarely referred to as such in the scientific or medical communities, because the term "amino acid," used without a qualifier, refers to the alpha amino acids, which GABA is not, nor is it incorporated into proteins.

http://en.wikipedia.org/wiki/Gamma-aminobutyric_acid